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Picked up a '78 LS1 swap project, have a couple of questions.

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Good afternoon,


I recently picked up a project Z locally. It has a iron block 5.3 mated to a TH350.


I am not a fan of the TH350 as without the overdrive I quickly run out of gear. It seems that the '78 had 3.5 gears already in the back so gearing it down isn't really that much of an option. I am considering the 700r4, and I understand I'll have to cut the driveshaft to fit it but having OD will be way better. The LS has the TH350 already on it so I won't need to purchase any spacers or conversion parts.


The other big thing I'm working through is the PO put a carb setup on it. While I am familiar with carbs I'd prefer to bring it back to Fuel Injection. I was considering the FI Tech complete setup as opposed to piecing together the original kit and paying for the wiring harness, megasquirt, and intake which comes to around the same cost as the FI tech setup.




Is there any advice for this, or other information I can look into?

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If you go back to efi you could run a 4L60E or better yet the 4L80...they are plentiful and work with almost all oem and aftermarket engine management setups. 


Stock intake and harness and stuff could be had dirt cheap and offers plenty of options...and the carb setup is worth some $$.


You could also sell your TH350 conversion stuff (if that is a thing I'm not familiar) and the carb setup for some good cash and almost come out even I bet.


I had the stock 4spd in my 78 (same 1:1 high gear as your TH350) and with the 3.54 gears it wasn't bad at all. LS motors like to rev and are fairly efficient at higher rpms if there isn't much of a load on them. For these reasons with my 4.8 swap I stuck with a 1:1 top gear transmission and it kept the cost way down. 


just my $.02 

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Yeah I do realize I have a lot more research to read. I do think that the 4L80E might be the best option over the 700r4 with looking into going back to efi. How well does working with the stock computer and Datsun go? Don't you need to buy a rather spendy wiring harness?


Caution on the 4L80E as you can make them fit in a 280z it is not the most enjoyable thing to do. Also you will need a custom trans mount as I don't believe there is one out there.

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Yea I have no idea if the 60e or 80e will actually fit in a stock z trans tunnel I was just throwing ideas out there not speaking from experience. I've only messed with manual transmissions in s30s. 


I modified a stock EFI harness in my z, it isn't bad at all. You can have the stock computer tuned to remove vats and modify any other parameters to get it running cheap, I sent mine to a guy on EBay for $45, had it running 2 days later.


This is an extremely helpful site: http://lt1swap.com

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Just an FYI, the 700 R4 and 4L60E are the same.  Turbo 350 with over drive.  4L80E is the 400 with over drive.  If you plan to do the 4L60E I would try to find a harness or pull one from a car that has the LS1 and the transmission.  They all come together at the computer harness and the chassis harness is tied in with the underwood fuse panel.  So if you can find a wrecked car with the engine and trans gone but the harness there it will make things a lot easier.  There are other options, run the stand alone EFI, we have used Powerjection in the past with good results and then get a stand alone for the 700r4 or the 4L60E  


Before I did anything I would spend an entire day on LS1 tech or any of the other LS dominated boards.  It is very easy to overlook a lot of stuff very easily.  Get a plan and stick to it.  JMHO, Richard. 

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And remember if you get a fly by wire style intake make sure to get the TAC module (little computer for the gas pedal) and the pedal assembly along with the short harness between the two!! 


You can easily retain DBW and modify the gas pedal to fit nice in your 280 just as I did. Keep in mind if you go with a truck intake you will probably have clearance issues with the hood and won't be able to run a strut brace.


Also it is good to know that if a factory computer is set up for fly by wire, it can't be converted to run without it, and vise-versa according to that LT1 website. You'd have to find a different pcm that was intended for the throttle body style you want to use. The harness is also a lot different.

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  • 1 month later...

I replaced my th350 with a 700r4 narrow K case, the K case is from a 4 wheel drive and is thicker at the bell housing and only as wide as the engine block. The narrow case has way more room for the exhaust and my 700r4 was 5/8in shorter than the th350 i have so I still have the same drive shaft. I bought a stage 2 build from patriot transmission in July 14, hooked up my odometer for the first time and went from 28,000 miles to 92,000 miles with no problems. The transmission was $1,000. I saw it on ebay but called direct and even though shipping was free I drove to Ocala from Venice and picked it up. My 700r4 uses a tv cable that hooks to carb like the kick down cable like th350.

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  • 3 months later...

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